Microorganisms, particularly fungi including mold and yeast, are widespread in nature and their growth is facilitated by moderate temperature and high humidity. They cause heavy loss in stored seeds of all kinds. Cereal grains, oilseeds and tubers comprise the main foods and feeds of the world today. Following harvest these agricultural commodities are stored in bulk for some time before they are processed for food or feed. The processed material is often stored in bulk as well. Various molds such as Aspergillus, Penicillium and Rhizopus invade both the stored seed and the products made from it, and thus cause heavy losses. Estimates of the extent of loss for cereal grains range from 0.5-10% of the world's production. A solution to this problem would certainly have a major impact on the world food shortage.
Apart from the damage caused to cereal grains there is a considerable health hazard from fungal attack of food and feedstuff. Certain molds under appropriate conditions of temperature and humidity would produce mycotoxins of which the best known example is aflatoxin which is produced by Aspergillus flavus. Aflatoxin growing on peanuts, wheat and various cereal has been shown to cause illness to domesticated animals. It produces hepatic cancer in several species including rats and trouts. Also it has been implicated with liver cirrhosis in children. Aflatoxin is a major problem to the poultry industry because of its growth retarding effect on the young birds.
Among the products made from cereal grains bread and cakes are most commonly spoiled by mold. The main species involved in the spoilage of bakery products are Rhizopus nigricans, Penicillium expansum, Aspergillus niger, and Monilia sitophila. Practically all commercial flours are infected by mold to a certain degree. These molds, however, are killed during baking; but as soon as the freshly baked product comes out of the oven fungus spores fall on it and subsequently multiply. In addition to molds, there is also the problem of ropiness in bread because of certain species of Bacillus. According to a survey by the baking industry, the U.S. consumers loose several million dollars a year from spoiled bread.
The fungal problems with cereal grains, flour and baked products is very serious in the tropical countries. They contribute to malnutrition and many health hazards in the developing world. In the industrialized nations, fungal problems in stored feed often result in major economic losses. Several additives such as propionic acid and propionates, caprylic acid, acetic acid, dehydroacetic acid, benzoic acid and benzoates, monochloracetic acid, sorbic acid and sorbates have been suggested to prevent fungal attack of cereal grains, feedstuff, and bakery products. However, so far only the propionates have been used to any great extent. One major disadvantage with propionates, sorbates, and the benzoates is that their antimicrobial activity is dependent upon acidic pH (Sauer, F. "Food Technology," 31, pp 66-67, 1977) while most food and feed materials are at about neutral pH. Acidification of food or feedstuffs to optimize the effectiveness of these additives make the products unplatable, whereas at neutral pH the amount of additive requirement is substantially increased. Ultraviolet light has been used to prevent fungal comtamination with limited success. Recent interests for alternate means of preventing fungal contamination is evidenced by U.S. Pat. Nos. 3,934,045; 3,971,855; 4,083,999 ; and 4,123,552.
There are other food products that are susceptible to mold spoilage. These include fresh fruits and vegetables, dairy products, margarine and intermediate moisture products such as meat patties, smoked meat and fish, pet foods, cheese, dry fruits, jams, etc. The genera mainly responsible for the spoilage of vegetables and fruits include Fusarium, Rhizopus and Alternaria. Several chemicals have been suggested to control fungal spoilage of fruits and vegetables. These include zinc carbonate. crotonic acid, esters of vanillic or parabenzoic acid and biphenyl. For intermediate moisture products, the preferred additives are sorbic acid or potassium sorbate. There have been however many attempts to improve these methods as evidenced by recent U.S. Pat. No. 4,048,342. Sometimes for products like cheese, wrappers are impregnated with antimycotic chemicals such as benzoate, methyl and propyl parabens, caprylic acid, o-phenylphenol and dimethylolurea.
There are many non-food products which are also susceptible to mold. All wood is subject to fungal decay whether it is in the form of boats, beer barrels, bridges or bungalows. The so-called dry rot and wet rot of woods are caused by Serpula lacrymans and Coniophora cerebella respectively. The preservative often used for treating wood is creosote. Agricultural plants such as canes and chestnuts that are used in making furniture or fiber board are also susceptible to fungal attack. The result of such attack is a reduction in the quality of the plant material and the possibility of it being useless. Recently in U.S. Pat. No. 3,928,620, a combination of propionic acid and hydrocarbon mineral oil has been suggested to protect such material from microbial attack.
Other non-food products that are decayed by mold include leather goods, fabrics and canvas materials, twines and sandbags, books and bookbinders, paints, gums and glue, electrical insulation, rubber linings and conveying belts. There are also many cosmetics and drug preparations that require preservation from fungal attack. Typical examples would be skin creams, lipstick compositions and toothpaste. Several chemicals are incorporated or sprayed upon in order to preserve these products. The list of chemicals include o-phenylphenol, biphenyl, methyl paraben and propyl paraben. These and similar chemicals are also used as disinfectant spray to control machinery mold in industrial installations and to prevent mold and mildew in house-hold operations.
Living tissues of plants as well as of animals including human are susceptible to fungal attack. Plant diseases caused by fungi are multitudinous. The Irish potato famine of 1845-49 was caused by the species Phytophythora infestans which destroys foliage of the potato plant and also rots the tubers during storage. `Blue mold` of tobacco is caused by the fungus Peronospora tobacina which destroys the leaves or, if the disease is not severe, reduces quality of the crop. `Coffee rust` is caused by the fungus Hemileia vastatrix which attacks the foliage of coffee trees, causing the leaves to become desiccated and to fall prematurely. The resulting effect is a very poor coffee crop. Although coffee is not a major food crop the effect of H. vastatrix can be devastating on the economy of many countries that are heavily dependent on coffee.
The majority of human fungal diseases are caused by dermatophytes or `ringworm fungi` which attack keratin-rich tissues namely the skin and hair. Most dermatophytes belong to two closely-related genera, Microsporum and Trichophyton. `Ringworm of the scalp` particularly in children, is caused by two species of Microsporum. `Athlete's foot` an infection that is familiar to most people is caused by Trichophyton mentagrophytes or T. rubrum. The warm and humid conditions of the feet facilitate fungal attack, particularly in the webs between the toes. The medicines used against ringworm and athlete's foot are griseofulvin and preparations containing Zinc undecylenate, Undecylenic acid, orthochloromercuriphenol, benzoic acid, solicylic acid, propyl paraben, etc.
The present applicant recognized the widespread detrimental effects of microorganisms as described above through personal and professional experiences and devoted considerable time to develop antimicrobial agents through screening of large numbers of chemicals.